Magnetic testing device.



T.J.MURPHY.

MAGNETIG TESTING DEVICE.

APPLIGATION FILED SEPT. 25, 1912. RENEWED JULY 17, 1914.

1,129,584. Patented Feb. 23, 1915.-

INVENTOR I up THOMAS JOSEPH MURPHY, OF ROCHESTER, NEW YORK ASSL NOR'OFONE-HALF TO JAMES B. D UFFY, OFROCHESTER, NEW YORK".

maenm'rc 'rns'rme DEVICE.

Specification or Letters Patent;

Application filed September "as, 1912; Serial No. 722,1eq, Renewed July17, 1914. Serial No. 851,646.

To all whom it may concern Be it known that I, THOMAS J osnrn MUR- RHY,asubject of the King of Great Britain,

and a resident of Rochester, New York, have invented a new and usefulImprovement in Magnetic Testin Devices, of which the following is aspeci cation.

My invention relates toa means for determining the character of amagnetic body as compared with another magnetic body.

It particularly relates to a means for determiningthe degreeofuniformi-ty of the steel composing steel rails. Steel rails havefrequently blow holes or crystallized portion, or portions that aresofter than the rest of the rail which sometimes causes fractures whenthe rails are under unusual strain.

The object of the invention is to test the rails and determine itscharacter with respect to some standard.

By my invention a means is provided for repeatedly and rapidlyimpressing upon one or more coils s'urroundingthe magnetic substance 25or substances to be tested, an electromotive force which suddenlychanges in its intensity. The lag of the current in a coil surroundingthe substance, due to the counter-electromotive force produced by theself-induction of the coil and the substance is utilized in determiningthe'relative condition of the substance tested. The lagof the currentresult!v ing from the impedance of one part of the circuit is comparedwith the lag of the current produced by the impedance of another part ofthe circuit. The indication of the difl'erence of the conditions foundin the 'substance tested and a standard will be accen-' tuated if a pairof coils are located about the substance tested and another pair arelocated about a standard of some'kind andthe coils of each pair areplaced in the opposite arms of a Wheatstone bridge and a ballisticgalvanometer or other electric indicator is In the drawings, Figure 1illustrates the construction selected. Fig. 2 shows in aconventional-way the electrical connections between the parts of thesystem. Fig. 3 shows the relation. of the coils to the rails. Fig. 4.

indicates the intensity of the magnetic flux" in the top of the frames.The rollers 7 are connected with worm wheels 16' and 17 which areoperated by the screws 18 and 19 located upon the shaft 20. The shaft ismounted inthe bearings 21, 22 and 23.. A worm wheel 24 is connected'tothe end of, the shaft 20. It is operated by the worm 25 which isconnected to the electricmotor26.

When the motor rotates the rails are carried through the coils 3, 4, 5,and 6 by therotation of the wheels 16 and 17. Variationsof the speed ofthe rails may be obtained by varying the speed of the motor by means ofrheostat. The coils 3, 4., 5, and 6 are mounted in l p-rights 30 and 31.U-shaped pieces 32 are secured to the inner coils and to the inner sidesof the outer coils and thereby securing the coils'together. SimilarU-shaped pieces 33 are secured to'the outer coils and 'to the up-rights31.

If desired. the inner coils 1 and 6 may be made oval, or they may bemade a' little smaller than the outer coils in order that they may belocated within'the outer coils. The coils are located inplanes atrightangles to 'each'other to-pre'vent mutual induction. vThe'arrangeinenttends to spread the flux, of the magnetic lines of forceand direct its axis across the length. of

' the rail, the magnetic axis being located between the coils and thepoles arranged as indicated when the potential of the current ismagnetic centers or across the magnetic axis of the two coils. The fieldwill vary accord, ing to the condition- 0f the steel of the rail locatedin the articular part through which the lines of. orce of the fieldpass. If 'a.=

A Y L 'of one. kind. The rail is' moved along the I fluctuating current' is used, the current through one pair will lag more than throughthe other.

Because' of the difl'erence in inductance in the two parallel circuitsthey will diii'er in the time required in whichthe currents may be builtup. This diiference'may be detected b any suitable electrical device,such asa bal istic galvanometer 40, which is connected to points Hand 42of the bridge.

The rail may be moved according to the frequency of the fluctuations ofthe current 7 used. .If the fluctuations are frequentthe a are connecterail may be movedtrapidly through the [coils by means of-theelectricmotor 26.

Fig. 2 indicates the electricalconnections.

between the arts of the system. The coils d in a Wheatstone bridge. The

coils located around the parts of therail I compared are connected inopposite 1e the; ridge so as to distort the ratio 0 the bridge if thereis any variation in the magnetic susceptibility of the rail. If the.per.- meability of the rail or the hysteretic losses should be abnormalat any par'tsurrounded '-the-. current to flow ,into'the bridge'when a Mvariable oran alternating current has reached its maximum; The potentialwill then. suddenly rise in all of the coils but the currentv willlag'behind according to the self-induction of the coils; In the systemshown in Fig.2, the bridge. is connected at-43 and 44 with the source offluctuating current. A half wave rectifier wherein the current may.bejs'tarted at a predetermined time in the wave of the impressedpotential .bycausing aspark to-jump across a pair of electrodesfand'which permits an impressed current to establish an arc across theelectrodes at the top of the wave,"is exceedingly elficient,- as itimpresses a sharply risingpotential on the circuit of the coils. Thebridge is connected to the. electrodes" 45.

The electrode 46 is connected to the sec- "ondary coil 47. The point 44of the'bridge is also connected tothev coil 47. The secondary 47receives its current from the coil 48, which'is connected to theterminals 49 a'nd'50 of theline. The rheostat 56 may be used to vary thespeed of the-motor and regulate themovement of the rail according to thefrequency of the current. A means is provided for starting an arebetween the electrodes. It consists of a means for producing. an;oscillatory discharge of a condenser across,'pr'eferably, two gaps inthe circuit of the condenser. One ap is between the electrodes 45 and 46an the other is between the parts of a suitable device only at desiredtimes or points in the wave of the current produced in the secondary4.7. I have shown an electric valve 51. It is connected .to thecondenser 52. The electrodes which causes the condenser to be discharged7o 45 and 46 are-connected between the valve 51 and the condenser 52.The condenser 52 is charged with a high potential charge by thesecondary coil 53 in which is induced a current by. the prima 54.- Theprimary 54 receives its current i'om the coil 47 of the line transformenI In Fig. 5 is shown conventionally theimpressed electromotive forcewave. -The spark across the electrodes 45 and46 is started at the pointmarked 61, preferably theapex or top of the wave. The current 63,immediately beginsto flow and rapidly .increases in both branches 43, 41and '44 and 43, 42, and 44 of the bridge. They have the same startingpoint but owing to difi'erence in impedance of the two parallelcircuits,

they will lag with respect to the current 62 that would normally passthrough thecircuit without any magnetic material in the coils. Thepotentials of thetwo branches at the points 41 and 42 will varyaccordingto the distortion of the ratio of the balance by the impedance ofthecoils located in opposite sides of the bridge. The potential waveunpressed upon the receiver may change-sign due to the remanence'ofhysteretic curves, the counter electromotive force and. the extracurrent being varied by the rate of change of the lines of force setupin the coils. This may be indicated by the curves 64 and 65 which willbe very readily detected by the telephone receiver.

The form of the construction in the drawings shown and described hereinand which contains the invention maybe greatly varied and theconnections may be greatly altered and yet the construction andarrangement will still. contain the invention. 4

What I claim is new and desire to secure by Letters Patent is as followslaIn an indicator the combination of a pair of coils adapted to belocated around a magnetic substance, a second pair of coils adapted tobe located'around a second magnetic substance, the said coils beingconnected' so as to constitute opposite arms of a Wheatstone bridge andmeans for impressing a pulsating current upon the bridge at points eachlocated between two coils belonging to different pairs;

2. In an indicator the combination of a pair of coilsadapted to belocated around a part of a rail, a second pair of coils adapted to belocated around a magnetic substance, the coils of each pair b e'ingconnected so as different pairs, and means for moving the rail throughthe said first named coils.

3. In an indicator the combination of a pair of coils adapted to belocated around a part of a rail. a'second pair of coils adaptl to belocated around a standard rail, the

coils of each pair being connected opposite so as to constitute the armsof a VVheatstone bridge, means. for impressing a pulsating current uponthe bridge at points each located between two coils belonging todifferent pairs, and means for moving the first rail through the firstnamed pair of coils.

4-. In an indicator the combination of a pair of coils adapted to belocated around a. rail and at right angles to each other, a second pairof coils, the coils of each pair being connected so as to constitute theopposite arms of a heatstone bridge, means for impressing a pulsatingcurrent upon the bridge at points each located between two coilsbelonging to difl'erent pairs of coils, and means for moving the railthrough the said first named coils.

5. In an indicator the combination of a pair of coils, a second pair ofcoils adapted to be located around a magnetic substance, the coils eachpair being connected so as to constitute opposite arms of a Wheatstonebridge and means for impressing a pulsating current upon the bridge atpoints located between one of each pair of coils.

6. In an indicator the combination of a pair of coils, a second pair ofcoils adapted to be located around a magnetic substance, the said coilsbeing so connected as to constitute the arms of alVheatstone bridge, arectifier of electric alternating currents connected to the saidbridgeat points located between one of each pair of coils.

'7. In an indicator the combination of a coil adapted to be locatedabout a rail, a

standard coil, means for producing a pulsat-v coils and an electric1ning current in said dicating means adapted to determine the lag ofcurrent produced by the magnetic condition of the rail, means forcontinuously moving the said rail through the said first named coil.

8. In an indicator the combination of a coil adapted to be located abouta rail, means for moving the rail through the said coil, :1. source ofpulsating current connected to the said coil and an electric indicatingmeans adapted .to indicate'variations of the lag in the said coil as therail is moved with respect to the coil.

In testimony whereof, I have signed my name to'this specification in thepresence of two subscribing witnesses.

THOMAS JOSEPH MURPHY.

Witnesses:

ROBERT B. CooHmNn, B. P. WAYNE.

